Reception system for local coils of a magnetic resonance imaging system
An apparatus, a magnetic resonance imaging system, and a method of use are provided for a reception system for transmitting magnetic resonance signals from local coils to an image processing unit of a magnetic resonance imaging system. The apparatus includes an analog receiver for receiving and processing analog signals from the local coils that is configured to directly sample analog signals having different individual frequency bands and/or frequency band pairs, to distinguish the analog signals and to process them differently. The apparatus also includes an A/D converter for converting the processed analog signals from the local coils into digital signals. The apparatus further includes a digital signal processor for processing the digital signals, wherein the digital signal processor includes a Weaver unit and a downstream decimation filter unit.
1. An apparatus for a reception system for transmitting magnetic resonance signals from local coils to an image processing unit of a magnetic resonance imaging system, the apparatus comprising:
an analog receiver for receiving and processing analog signals from the local coils, the analog receiver configured to directly sample analog signals having different individual frequency bands, frequency band pairs, or frequency bands and frequency band pairs, to distinguish the analog signals and to process the analog signals differently;
an analog/digital (A/D) converter for converting the processed analog signals from the local coils into digital signals; and
a digital signal processor for processing the digital signals, the digital signal processor comprising a Weaver unit and a downstream decimation filter unit (DFE).
2. The apparatus as claimed in claim 1 , wherein the analog receiver comprises an input diplexer having a highpass path and a lowpass path,
wherein the highpass path of the input diplexer comprises a changeover switch for feeding back a local oscillator frequency to the input diplexer and then to the local coils,
wherein adjoining downstream of the changeover switch is a bandpass path comprising a bandpass amplifier and a bandpass filter,
wherein adjoining downstream of the lowpass path of the input diplexer is a lowpass path comprising a lowpass amplifier and a lowpass filter,
wherein signal outputs of the bandpass filter and the lowpass filter are connected for signaling purposes to an input of the A/D converter via a common summation point.
3. The apparatus as claimed in claim 2 , wherein the A/D converter comprises a decimation filter unit comprising a decimator lowpass filter and a decimator, the decimator configured to output one or more of the frequency bands converted by sampling at 80MS/s or a frequency-unchanged frequency band pair of the digital signals at a reduced data rate.
4. The apparatus as claimed in claim 3 , wherein the digital signal processor is configured to isolate the frequency bands of the frequency band pairs from one another and to convert a frequency of the frequency band pairs and the individual frequency bands and to reduce the data rate.
5. The apparatus as claimed in claim 4 , wherein the Weaver unit of the digital signal processor comprises two Weaver signal paths, wherein each Weaver signal path comprises a first 90° quadrature mixer, a downstream frequency filter, a downstream decimation chip, and a downstream second 90° quadrature mixer.
6. The apparatus as claimed in claim 5 , wherein the first and second 90° quadrature mixers of the decimation filter unit are configured to convert frequencies of the signals from the frequency band pairs and to retain the frequency of the frequency band.
7. The apparatus as claimed in claim 1 , wherein the A/D converter comprises a decimation filter unit comprising a lowpass filter and a decimator, the decimator configured to output one or more of the frequency band converted by sampling at 80 MS/s or a frequency-unchanged frequency band pair of the digital signals at a reduced data rate.
8. The apparatus as claimed in claim 1 , wherein the digital signal processor is configured to isolate the frequency bands of the frequency band pairs from one another and to convert a frequency of the frequency band pairs and the individual frequency bands and to reduce a data rate.
9. The apparatus as claimed in claim 1 , wherein the Weaver unit of the digital signal processor comprises two Weaver signal paths, wherein each Weaver signal path comprises a first 90° quadrature mixer, a downstream frequency filter, a downstream decimation chip, and a downstream second 90° quadrature mixer.
10. The apparatus as claimed in claim 9 , wherein the first and second 90° quadrature mixers are configured such that the digital signals from one or more of the individual frequency bands or the frequency band pairs are mixed with an oscillator frequency that corresponds to one quarter of a mixer clock rate.
11. The apparatus as claimed in claim 9 , wherein the frequency filters are in the form of switchable lowpass filters or bandpass filters, wherein the bandpass filter comprises a cascade comprising a lowpass filter and a highpass filter, wherein the lowpass filter is a decimation filter and the highpass filter is arranged downstream of a decimation stage and operates at a reduced clock rate of 20 MS/s.
12. The apparatus as claimed in claim 9 , wherein the decimation filter unit of the digital signal processor is connected downstream of the Weaver unit and comprises a first DFE signal path and a second DFE signal path in the decimation filter unit, wherein each DFE signal path comprises a frequency filter, a downstream decimation chip, and a downstream mixer.
13. The apparatus as claimed in claim 12 , wherein the two Weaver signal paths are configured to channel added digital signals from the two Weaver signal paths out of a first Weaver signal path of the two Weaver signal paths and subtracted digital signals from the two Weaver signal paths out of a second Weaver signal path of the two Weaver signal paths into a respective DFE signal path.
14. The apparatus as claimed in claim 13 , wherein the two DFE signal paths are configured to feed the added digital signals from the two Weaver signals paths into the first DFE signal path of the two DFE signal paths and the subtracted digital signals from the two Weaver signal paths into the second DFE signal path of the two DFE signal paths.
15. The apparatus as claimed in claim 12 , wherein the two Weaver signal paths are configured to separate the frequency band pair entering the Weaver unit and to channel individual signals out of the first Weaver signal path and the second Weaver signal path, respectively, and to channel the individual signals into the first DFE signal path and the second DFE signal path, respectively.
16. The apparatus as claimed in claim 12 , wherein the frequency filters of the decimation filter unit are lowpass filters.
17. The apparatus as claimed in claim 1 , wherein a first 90° quadrature mixer and a downstream second 90° quadrature mixer of the decimation filter unit are configured to convert frequencies of the signals from the frequency band pairs and to retain a frequency of the frequency band.
18. A method for operating an apparatus for a reception system for transmitting magnetic resonance signals from local coils to an image processing unit of a magnetic resonance imaging system, the method comprising:
receiving and directly sampling, by an analog receiver, analog signals from the local coils, wherein the analog receiver directly samples analog signals having different individual frequency bands, frequency band pairs, or frequency bands and frequency band pairs, to distinguish the analog signals and to process the analog signals differently;
processing the analog signals by a digital signal processor having a Weaver unit and a downstream decimation filter unit; and
converting the processed analog signals from the local coils into digital signals, by the digital signal processor, wherein the frequency bands of the frequency band pairs are isolated from one another, and wherein a frequency of the frequency band pairs is converted and data rates thereof are reduced.
19. A magnetic resonance imaging system comprising:
local coils;
an image processing unit; and
an apparatus for a reception system for transmitting magnetic resonance signals from the local coils to the image processing unit, wherein the apparatus comprises:
an analog receiver for receiving and processing analog signals from the local coils, the analog receiver configured to directly sample analog signals having different individual frequency bands, frequency band pairs, or frequency bands and frequency band pairs, to distinguish the analog signals and to process the analog signals differently;
an analog/digital (A/D) converter for converting the processed analog signals from the local coils into digital signals; and
a digital signal processor for processing the digital signals, the digital signal processor comprising a Weaver unit and a downstream decimation filter unit.